There has been conventionally known a printer of an electrophotographic type, in which a developing cartridge is detachably mountable. The developing cartridge includes a frame, various rollers including a developing roller, and a gear mechanism. The various rollers are supported in the frame. The gear mechanism is provided on an outer surface of a side wall constituting the frame.
One developing cartridge has been proposed as the above-mentioned type of developing cartridge. In this developing cartridge, the gear mechanism includes an input coupling and a detection gear. The input coupling is for receiving driving force for driving the various rollers. The detection gear is for detecting whether the developing cartridge is a new one or a used one. Support shafts, including an input coupling shaft and a developing roller shaft, protrude leftwardly from a left side wall constituting the frame. The gear mechanism is supported on the support shafts.
In order to produce this developing cartridge, the rollers, the gear mechanism, and the other members are assembled onto the frame that is provided with the support shafts.